At present, an increasing number of display modules require a limitation on the observation angle for the purpose of anti-peeping. The existing anti-peeping technology is to add an anti-peeping function at an emitting layer of the organic electroluminescent device. The process of adding the anti-peeping function at the emitting layer must be performed within a processing chamber. However, as a boiling point of carbon is 4827° C., an excessive process temperature is likely to affect properties of a functional layer which has already evaporated on a substrate, finally affecting performances of the organic electroluminescent device.